It is known to provide vibrations to the skull bone directly or indirectly in order to exitate the cochlear whereby this excitation may be perceived as sound. This is done to provide a sensation of hearing to people who has a functioning cochlear, but have damaged or deformed ear structures.
It is known to provide hearing to these patients by attaching a magnetic means to the skull bone surface under the skin, and then excite the magnetic means with a magnetic field corresponding to a sound signal. Also a magnet provided subcutaneous may serve as an attachment point for a conventional vibrator which will be sitting exteriorly on the skin, attached thereto by the subcutaneous magnet. In both these instances, the skin between magnet and the exterior part may be subject to compression forces, and this may hamper blood circulation in this skin layer and serious negative effects such as irritation and necrosis may result from this.
Yet a further prior art example is to attach a vibrational transducer subcutaneously to the skull bone or cochlear and to energize the transducer by means of an electromagnetic signal provided by an externally mounted apparatus. In this kind of apparatus, a transcutaneous transmission of both energy and signal is necessary from the device on the outside to the transducer placed at the cochlear or under the skin, and a coil or similar device is needed to receive the energy and information signal.
In a prior art device disclosed in U.S. Pat. No. 5,176,620 the transducer is provided under the skin behind the ear, and an acoustic wave guide is provided between the transducer and the cochlea. In this way, the skull bone is not used as transmission path, and the transducer may be made smaller and may consume less energy in order to vibrationally excite the cochlea. However, in this prior art device the power signal is still to be transmitted through the skin as an electromagnetic signal, and a complicated transducer with a multitude of electronic components must be provided in or at the skull bone.